1. Field of the Invention
The present invention is directed to polyhydroxyalkyl oligoureas, polyether polyols obtained by alkoxylating the polyhydroxy alkyl oligoureas and the use of both of these products for the production of isocyanate polyaddition products, particularly rigid foams.
2. Description of the Prior Art
A variety of starter molecules have previously been described for the production of polyols for the isocyanate polyaddition process, depending upon the desired functionality. The properties and molecular weight thereof are then adjusted by the addition of predominantly oxirane derivatives.
Starts for these polyols include diols, triols, like glycerine, trimethylolpropane, pentaerythritol, sucrose or glucose. However, urea has also been used as a starting molecule as described, for example, in FR-P Nos. 7,700,831, 7,624,154, 947,847, BE-P No. 678,064 and U.S. Pat. No. 4,180,131. In comparison with high functionality starters, urea has the disadvantage of having a low functionality which is generally about 2.
Hydroxyalkyl mono ureas have been described as incorporabel flame-proofing agents for polyurethane integral foams in the German Offenlegungsschrift No. 3,332,794.